This is a proposal to extend the Rancho Bernardo Study (RBS) of osteoporosis in order to prospectively examine sex specific rates and risk factors for bone loss and fracture (clinical and vertebral) in older adults. Nearly 1500 men and women aged 55 and older were studied in 1988- 1991 and again in 1992-1995 under a MERIT award, when they were characterized for multiple behavioral, biological and genetic risk factors for osteoporosis and had measurements of bone mineral density (BMD) at the hip and spine obtained four years apart. RBS is the largest prospective community-based study of osteoporosis in the United States in which men and women were studied concurrently using dual energy x-ray absorptiometry (DEXA). Work to date shows striking similarities in accelerated bone loss in the older men and women (greater than or equal to 75 years of age) over four years, and striking differences in the association of BMD with diabetes, insulin IGF-1, and serum testosterone. The cause of gender differences (and their absence) can provide new insights into the etiology, prevention and treatment of osteoporosis in both men and women. In the present study, 550 men and 650 women (>60% aged 70+ years) will have repeat evaluations for selected risk factors and bone turnover markers, repeated BMD measures at the hip and spine; repeat radiographs of the thoracic and lumbar spine; continued follow-up for new clinical fractures; reassessment of functional status, quality of life and fall- related co-morbidities (including vision, cognition, and muscle strength); and first time evaluation of 25 OH vitamin D; 1, 25 (OH)/2 vitamin D, intact parathyroid hormone, and selected measures of bone size and geometry. This study was designed to provide (1) measures of BMD over a 10 year interval, necessary to determine the timing, frequency and antecedents of accelerated bone loss in both men and women, and (2) continued follow-up for fractures, necessary to provide adequate numbers of vertebral fractures and clinical fractures to determine fracture risk, risk factors, and consequences in both sexes.